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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:4
UID:UW-Physics-Event-9548
DTSTART:20260114T190000Z
DTEND:20260114T210000Z
DTSTAMP:20260413T102613Z
LAST-MODIFIED:20260114T171847Z
LOCATION:5280 Chamberlin
SUMMARY:Tokamak Plasmas above Traditional Density Limits in the Madiso
 n Symmetric Torus\, Preliminary Exam\, Joseph Flahavan
DESCRIPTION:Recent experiments in the Madison Symmetric Torus (MST) ha
 ve demonstrated the capability of sustaining stable tokamak plasmas wi
 th densities far above the Greenwald limit\, up to 18nG. The Greenwald
  limit\, nG\, is an empirically determined upper limit on the line-ave
 raged electron density for stable operation of current-carrying toroid
 al laboratory plasmas\, including tokamaks. Fusion power increases wit
 h density\, making it of interest to determine the nature of MST’s a
 bility to operate without disruptions at densities far greater than th
 e conventional limit.
\nWhen the electron density approaches 2nG\, a d
 istinct equilibrium develops with broadened electron density and nearl
 y flat current density profiles. This happens to occur near the Sudo l
 imit\, nS\, an empirical density limit observed in stellarators that i
 s attributed to radiative collapse and is dependent on input power.
\n
 Here\, I present direct measurements\, profile reconstructions\, and f
 luctuation analysis across the range of densities that has been access
 ed in MST tokamak plasmas\, 0.5 < ne/nG < 18\, with a focus on plasmas
  near nG and nS where changes in behavior are observed. Experimental r
 esults are compared to several different theoretical models of the Gre
 enwald density limit\, including those involving enhanced edge turbule
 nce or radiation-destabilized tearing modes.
\n
URL:https://www.physics.wisc.edu/events/?id=9548
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